Electric furnace



V: J. CHAPMAN ELECTRIC FURNACE Oct. 11 1927.

Filed March 26 1925 Inventor; \/er'ni J. Chggmaq U :Z His Attorneg.

Patented Oct. 11, 1927.

UNETED STATES PATENT OFFICE.

VERNI J. CHAPMAN, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEXV YORK.

ELECTRIC FURNACE.

Application filed March 26, 1925.

My invention relates to electric furnaces, more particularly toelectric furnaces provided with one or more electrodes for gener ating heat, and has for its object the provision of an improved electrical connection for the electrode.

In certain electric furnaces of the electrode type, particularly those adapted for three phase operation, an electrode is provided which is fixed in the bottom of the furnace crucible and extends upward into the furnace chamber'where it is in arcing relation with an upper adjustable electrode. It is customary to have, the bottom electrode project from the furnace to provide for the making of an electrical connection with it. This arrangement has the disadvantage that the electrode is exposed to oxidation, and furthermore dissipates an appreciable amount of heat.

In carrying out my invention I completely enclose the bottom electrode, and establish an electrical connection with it by means of a member of relatively high electrical conductivity which is in engagement with the electrode at a point. within the furnace wall.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a vertical section view of an electric furnace embodying my invention, while Fig. 2. is a fragmentary bottom plan view of the apparatus for making the electrical connection with the bottom electrode.

Referring to the drawing, I have shown my invention in one form as applied to an electric furnace comprising a heating chamber 10 formed by walls built from heat rcfractory bricks 11. the brick walls being enclosed in a metallic protecting shell or casing 12. Extending into the furnace chamher through the top of the furnace wall are two electrodes 13 and 14 made of a suitable material such as carbon or graphite. These upper electrodes are preferably adjustable in any suitable manner so that they can be fed into the chamber 10 as they are burned 1].11".

Each of the two upper electrodes cooperates with a lower electrode which is built into the bottom of the furnace. Only one of the bottom electrodes is shown. this being the bottom electrode 15 cooperating with the upper electrode 13. It will be understood that a similar bottom electrode is provided Serial No. 18,561.

for the upper electrode 14. The two bottom electrodes extend into the bottom wall of the furnace and terminate at a point near the'exterior of the bottom wall. As shown the electrode 15 is electrically connected by way of block 16 with a centrally located block 17, the lower end of which terminates within the furnace wall. 4 It will be understood that the bottom electrode cooperating with the upper electrode 14 is electrically connected with the block 17 in a similar manner. The blocks 16 and 17 are constructed of the same material as the electrode 15 and constitute a part of the'electrode 15. A suitable packing cement 16, such as a mixture of graphite and hot tar, is used to form the joints between the parts 15, 16 and 17.

The block 17 is provided with a conical recess 18 in which fits the tapered end 19 of a terminal member 20 of smaller cross-section, made of an electrically conducting material, such as copper. The terminal bar 20 projects from the shell 12 for'connection to a suitable electrical supply circuit. The terminal member 20 is sealed in the furnace wall by means of a suitable refractory non-porous cement 21, such as a mixture of fire clay and sodium silicate, which also insulates it electrically fromthe shell 12. Closely surrounding theterminal member is an insulating bushing 22 made of a suitable material, such as asbestos lumber, which is secured by means of bolts to the exterior of the shell.

It will be observed that the electrical connection between the terminal member 20 and the block 17, forming a part of the lower electrode, is made at a point within the furnace wall and that the block 17 is completely enclosed by the furnace wall and thus protected from oxidation. This arrangement furthermore conserves the heat generated in the furnace since the lower end of the block 17 is surrounded by heat insulating material. The loss of heat due to conduction through the terminal member 20, which has approximately the same conductivity as the electrode, is much less than would occur if the electrode itself projected from the bottom of the furnace. This is due to the fact that a copper terminal member having substantially the same electrical conductivity as the graphite or carbon electrode, has a much lower heat conductivity.

In order to hold the terminal member in close contact with the block 17 at all times,

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ll 'i f ii ili lrifiili i tc er itie s copper. barges notwithstaz iding the difference in the expansion and contraction of the two parts when heated and cooled, resilient means are provided for forcing the terminal member inward. This comprises a cross bar 23, made of a suitable insulating material, suchas asbestos lumber, which is in engagement with the outer end of the terminal member. Passing over the cross bar 23.is allshaped strap 24 having its ends bentou'tw'ard at right an les tq forn1 seats for lielicalspringsjfi an 26; Thelower ends of the springs. rest aga i nsjt. stops caried by bolts 27 and 28 h c r hrees 1 hQfiPYiPfi and. throughholes in the ends Qf the-strap 24 and are securedito tlie, ca 'si iig.l2. The sprangs and .26. ac ting on tlie 9.4: itirce. the terminal I member upward in close contact with the blocli '17. Asbestosj wasbersg f and 26 are. prqi'ided between; the lspringsand the. st ra' to reduce tlie c heat froin the l lq' lil nrw el of the eg k l -i irma mnn er in accordance withlt-lie a pa a tanagger: engnaga egto .fthose r e-Premi e eti oe e t e uter end mma m mb r! 0 ea -1 e m ie v and: 30l are secur ed to 1t. These ,bai's' andSBO. ar tilized in ,estab- The .oiite r gend of. t e terrnirral s' la 'i iesi fhei zha tlr att e -m na-ee sipge f'va'riogs mod fications section having one end in electrically conducting engagement with said electrode at a point within (1 wall. said terminal {NONI- "ntiall the same electrical iid electrode. and cooling the projecting end of said termi- .1. An electric furnace comprising a re frat-tor};- crucible, a carbonaceous electrode red in the Wall of said crnciiz-e. a metallic terminal member in engagement with said electrode at a point within said wall, and res-dic-ntmeans {or holding said terminal member in engagement with said electrode so as to :2: Kl electrical. contacthctween them. said to! lllQlHbCL'lltlYlllg snbstzuitiali the same. electrical condnctivitv said electrode.

4. An electric furnace comprising a retory crucible, an electrode secured inthe fltom of szgid crucible .a terminal member engagement with said electrodeata point w thin the wall of sai (l cruc 1ble, saicl ter inrnal member havmgsubstantially the same electrical eonduct' ityas said electrode, re.

silrentmeansfor holding said terminal member in engagement wjthsaid electrode,

and means forming a tight joint between said crucible. and said terminal,

good electrical conductivity projecting iron: sand crucible having its. inner end in 5. An electric furnace comprising a re fr a ctory crucib le,-a refractoryelectrode se outer end terminating in the interior of said wall, the outer end of said electrode being provided with a conical rec5s, a- 1netallic terminal member havingatapered end fitr cured inthe wall of said crucible havingits ting in; said recess, and ineansfopsecuring said tapere dcndj u. said rece so, asto main- :taiii good electrical contact between said.

cleetrodefaiul said terminal inelnber.

(i. An electric furnace congprisinga refrnclfir) crucible, an elccti odesecneed in th bottom of said crucible and enclosed therein. said electrode be ng pIQl'lClt!d .\VllLll a ifOlllCi'il recess a inctaliic terminal member harm-g a tapes .c res-went means for wre ngsaiu terminal member into said reces 50.:15 to uau tain a good electrical contact hchveenthcni upon-- expansion and contraction of said crucible,

and means fUl'lllilW a ti ht foint between.-

said terminal and said crucible.

In witness when-0L I have hereunto stetmy hand this 25th darof March. 1925.

V ERNI J. CHAPMAN ".l end fitting in said recess 

